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Let x be the number of card in a pack (assumed to be the same for the packs in this problem).
Write an equation as you read the problem
    x + 2 + 2x = x + 12   cards.
Simplify and find x
    3x + 2 = x + 12
    3x - x = 12 - 2
       2x  =    10
        x  =    10/2 = 5.
ANSWER.  There are 5 cards in each pack in this problem.
Solved.
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Today's morning tasks are much more reasonable than the usual ones at this time of a day.
The impression is as if the sun of reason shone in the east.